JS事件（五）事件委托

<ul id="ul">
    <li id="goSomewhere">goSomewhere</li>
    <li id="doSomething">doSomething</li>
    <li id="sayHi">sayHi</li>
</ul>

<script>
var ul=document.getElementById("ul");

EventUtil.addHandler(ul,"click",function(event){
    event=EventUtil.getEvent(event);
    var target=EventUtil.getTarget(event);
    switch(target.id) {
    case "goSomewhere":
        location.href="https://www.baidu.com";
        break;
    case "doSomething":
        document.title="I changed the title";
        break;
    case "sayHi":
        alert("hi");
        break;
    }
});
</script>

核心：利用冒泡原理，将事件绑定到父元素，减少内存消耗，提升性能

利用event属性找到事件源，将事件定位到具体元素上